Tropopause
Tropopause
The tropopause is the upper boundary of the troposphere , a layer of the earth's atmosphere near the ground. In the troposphere, the temperature generally decreases with increasing altitude, with restricted exceptions called inversions. However, at a height of about 6 mi (10 km) at the poles 9 mi (15 km) at the equator, the temperature abruptly becomes constant with increasing altitude. This isothermal region is called the stratosphere , and the interface between it and the troposphere is called the tropopause. Mixing of air across the tropopause is slow, occurring on a time scale of weeks on the average, while tropospheric mixing is more rapid.
The existence of the stratosphere is largely caused by the absorption of solar energy , mostly ultraviolet light, by oxygen to form ozone . The balance of the heating is caused by absorption of other parts of the solar spectrum by other trace gases.
See also Ultraviolet radiation